Thickness and in-depth composition profile of altered layer caused on CuNi alloy surface due to preferential sputtering

Abstract

Preferential sputtering on CuNi (50 wt%) alloy surfaces was studied by Auger electron spectroscopy. The CuNi (50 wt%) sample was prepared by electrolytically polishing the sample under some specific conditions so as to obtain a mirror surface and at the same time keeping the surface composition identical with that of the bulk. The average thickness of the altered layer produced on the CuNi surface due to the preferential sputtering has been estimated to be of the order of ~15 Å for normally incident 500 eV Ar ion bombardment according to the approach proposed by Ho et al. The individual sputtering yields of the constituent elements in the alloy have also been measured. The thickness of the altered layer and the individual sputtering yields in the alloy agree very well with those reported for evaporated Cu-Ni samples by Ho et al. It has also been found that the thickness of the altered layer decreases as the angle of incidence of sputtering ion beam increases. In-depth composition profile measurement of the altered layer has also been made according to the analysis reported by Watanabe et al., but paying particular attention to the estimation of signal intensities of the low energy Auger electrons (M 1M 45M 45 transitions). This mode of measurement has shown a higher enrichment of Ni on the sputtered Cu-Ni surface than those obtained from the high energy Auger signals.